This invention relates to structures for sealing the openings of containers to prevent leakage of the contents and particularly to prevent the escape of contents maintained under pressure.
Cans and jars used in preserving fruit, vegetables and other food products, as well as pressure cookers, and other like containers must be able to maintain a pressure seal when closed. A variety of jar and pot sealing structures are known. A conventional seal for a jar, such as might be used in home preserves, comprises a disk for covering the jar mouth and a ring for cinching the disk against the jar mouth. A sealing gasket is provided which is generally disposed between the disk and the jar mouth so that the tightening of the ring assures a sealing contact. In this type of sealing structure, any increase in internal pressure tends to loosen the seal, increasing the probability of leakage.
A number of sealing structures have been proposed to overcome the problem of potential leakage resulting from increased internal pressure. Representative patents known to address the problem are U.S. Pat. No. 645,430 to Smelker, U.S. Pat. No. 711,452 to Meyer, British patent specification No. 485,051 to Fritsch, U.S. Pat. No. 2,967,944 to Davies, and U.S. Pat. No. 3,687,333 to Burnett et al. Although many of the prior art structures are designed to provide a tighter seal as internal pressure increases, many do not provide a satisfactory seal under certain conditions of negative and neutral pressure.